As a chuck device arranged at a front end of an electric screw driver or the like, there has been conventionally proposed a chuck device having a lock mechanism which tightens and fixes a base shaft of an inserted rotating jig by pawls (jaws) from three sides to lock the rotating jig in a tightened state (see Patent Literature 1).
The chuck device includes an engaging ring with a shaft direction restrained relative to a chuck main body, and a holding ring movable in the shaft direction relative to a ratchet main body. Then, on opposed surfaces of the engaging ring and the holding ring, ratchet gears meshing with each other in a loosening direction are formed.
Accordingly, it is assumed that moving the holding ring in the shaft direction to make the ratchet gears of the engaging ring and the holding ring mesh with each other enables rotation, in a tightened and fixed state, to be restricted in a tightening release direction, thereby locking a tightened state.
However, when a rotating jig, locked in the tightened state by a lock mechanism, is rotationally driven for drilling or the like, in which state, a base shaft of the rotating jig is fixed by jaws from three directions, resonance or inertial force due to vibration might cause a rotation input body to rotate in the tightening release direction to carelessly release a rotation restricted state.